Accession Number : ADA312462

Title :   The Effect of High Freestream Turbulence on Film Cooling Effectiveness.

Descriptive Note : Final rept. 1 Nov 95-9 Jul 96,

Corporate Author : WRIGHT LAB WRIGHT-PATTERSON AFB OH

Personal Author(s) : Bons, Jeffrey P. ; Rivir, Richard B. ; Mac Arthur, Charles D.

PDF Url : ADA312462

Report Date : 16 JUN 1994

Pagination or Media Count : 20

Abstract : This study investigated adiabatic wall cooling effectiveness of a single row of film cooling holes injecting into a turbulent flat plate boundary layer below a turbulent, zero pressure gradient freestream. Levels of freestream turbulence (Tu) up to 17.4% were generated using a method which simulates conditions at a gas turbine combustor exit. Film cooling was injected from a single row of five 35 degree slant-hole injectors (length/diameter = 3.5. pitch/diameter = 3.0) at blowing ratios from 0.55 to 1185 and at a nearly constant density ratio (coolant density/freestream density) of 0.95. Film cooling effectiveness data is presented for Tu levels ranging from 0.9% to 17% at a constant freestream Reynolds number based on injection hole diameter of 19000. Results show that elevated levels of freestream turbulence reduce film cooling effectiveness by up to 70% in the region directly downstream of the injection hole due to enhanced mixing. At the same time, high freestream turbulence also produces a 50-100% increase in film cooling effectiveness in the region between injection holds. This is due to accelerated spanwise diffusion of the cooling fluid, which also produces an earlier merger of the coolant jets from adjacent holes.

Descriptors :   *TURBULENCE, *GAS TURBINES, *FILM COOLING, PRESSURE GRADIENTS, OPTIMIZATION, TURBULENT FLOW, TURBULENT BOUNDARY LAYER, TEMPERATURE GRADIENTS, FREE STREAM, FLOW SEPARATION, ADIABATIC CONDITIONS, REYNOLDS NUMBER, THERMAL STRESSES, BOUNDARY LAYER FLOW, CROSS FLOW, JET MIXING FLOW, DIFFERENTIAL THERMAL ANALYSIS.

Subject Categories : Fluid Mechanics
      Thermodynamics
      Jet and Gas Turbine Engines

Distribution Statement : APPROVED FOR PUBLIC RELEASE